Research Reports

Description:
The installation of loop detectors in portland cement concrete pavement (PCCP) may shorten affected panel life, thus prematurely worsening the condition of the overall pavement. This study focuses on the performance of loop embedded panels (LEPs) by analyzing pavement data collected by WSDOT, and comparing it to the overall pavement performance on I-5 in King County. The results were divided by non-rehabilitated, diamond ground and dowel bar retrofit and diamond ground PCCP, as was done in the reference paper, to facilitate comparison.

Overall, LEPs perform worse – regarding panel cracking – in comparison to loop free panels (LFPs), except on the small section of I-5 that has been dowel bar retrofitted and diamond ground. For the non-rehabilitated PCCP, the difference between LEPs and LFPs with 1 crack is less than 1% but more than twice as many LEPs have what is considered “failed” panels (2 or more cracks) than LFPs. This might indicate that the loop installation affects the severity of panel cracking more than being the cause for it.

Using these results and assuming panel replacement at the cost of $20,000 each, the cost of loop installation to the pavement was found to be $560 each. Traffic simulation was done for a section of I-5 to calculate delay due to lane closures, which loop detector installation requires. The user cost associated with the delay is a substantial part of the overall cost of loop installation: 40 – 60 percent, depending on the number of affected lanes on the freeway. If user costs are accounted for, the overall cost of video and loop detection systems can be comparable.